1. Field of the Invention
This invention relates to an apparatus for preventing chips resulting from cutting a workpiece with a machine tool and/or a cutting liquid from being scattered.
2. Description of the Prior Art
A problem with a machine tool is that chips resulting from cutting a workpiece are scattered, leading to the degradation of a working environment. When the machine tool uses a cutting liquid for cutting the workpiece, the cutting liquid is also scattered. Further, the scattered cutting liquid becomes mist, leading to the pollution of a surrounding environment.
In particular, addition of various additives to the cutting liquid has been recently conducted for the purpose of providing an improved machinability, an increased cutting accuracy, an extended life of a cutting tool and so on. As a result, although the improvement on cutting conditions and the reduction in cutting time or the like are attainable, rubber and resin-made parts of the machine tool are damaged under the influence of these additives, resulting in the development of defects in some cases.
In addition, how to reduce the effect on the environment with the increasing production is generally at issue. From this point of view, a demand for preventing the chips and/or cutting liquid from being scattered is increasing particularly in the field of cutting performed with the machine tool.
FIG. 11 is a view showing a general configuration of a conventional machine tool having been realized in consideration of prevention of the chips and/or cutting liquid from being scattered. In FIG. 11, there is shown an instance of a machine tool that employs a mist collector for collecting a misty cutting liquid.
A spindle head 2 is mounted to a column 1 through a translation guide 15 in such a manner as to be movable in an axial direction of a spindle 13. A spindle unit 14 is mounted to the spindle head 2. The spindle unit 14 has the spindle 13, to which one of various tools 4 exchangeable by a tool exchanger 3 is mounted. The tool 4 mounted to the spindle 13 revolves at various revolving rates together with the spindle 13 to make a relative movement with respect to a workpiece 6 in various manners suited to cutting modes, thereby cutting the workpiece 6. The workpiece 6 is fixed in place on a table 5 supported in such a manner as to be movable in two directions (X- and Y-axis directions) orthogonal to the axial direction (Z-axis direction) of the spindle 13.
The spindle head 2 has a plurality of nozzles 22. A cutting liquid pump 20 is adapted to feed a cutting liquid from a cutting liquid tank 11 to the plurality of nozzles 22 through a cutting liquid hose 21. The cutting liquid is discharged through the nozzles 22 from the side of the spindle 13 to a plurality of predetermined positions of the tool 4. The reason why the plurality of nozzles 22 is required is that an exchange of tools involves a choice of a suitable tool among a plurality of tools, so that the cutting liquid needs to be fed to proper positions depending on the shape of the chosen tool.
When the cutting liquid hits against the revolving tool, it scatters and then becomes misty. If the revolving tool is a small-diameter tool, the cutting liquid becomes relatively less misty. However, when a large-diameter tool such as a milling cutter is used, or the cutting liquid discharged through the nozzles 22 directed to the tip end of a small-length tool hits against a large-diameter holder part of a large-length tool, it is feared that the cutting liquid yields a large quantity of mist, which is then sent to the outside of the machine tool in a scattered manner.
In this connection, in order to prevent the cutting liquid from being scattered, a cutting section of the machine tool is covered with a splash guard 23, and a mist collector is provided to collect the scattered misty cutting liquid with a duct 25. The splash guard 23 has a door 24.
The door 24 is closed while the workpiece 6 is being cut. The cutting liquid pump 20 is adapted to feed the cutting liquid from the cutting liquid tank 11 to the plurality of nozzles 22 through the cutting liquid hose 21, and the cutting liquid is discharged through the nozzles 22 toward the revolving tool 4. In this manner, the tool 4 cuts the workpiece 6.
Streams of the cutting liquid running out of a cutting area and relatively large mass droplets of the cutting liquid and/or the chips are returned into the cutting liquid tank 11 along the inside of the splash guard 23. On the other hand, the finely misty cutting liquid is exhausted through the duct 25 placed at an upper part of the machine tool, together with air being drawn into the splash guard 23 through an opening provided in a lower part of the machine tool. Although not shown, a structure is adopted, in which the misty cutting liquid having been sent to the mist collector is drained into the cutting liquid tank through a filter and/or a centrifugal separator, thereby permitting circulation of the cutting liquid.
Use of the splash guard 23 may suppress the leakage of the resultant misty cutting liquid from the machine tool to the outer circumference thereof to a large extent, while the machine tool is continuously in operation. However, it is feared that the machine tool develops defects therein in some cases under the influence of the cutting liquid and/or the chips. In such a case and/or on termination of the cutting, the door 24 needs to be opened for setup of the next cutting. It takes much time to sufficiently ventilate air in the machine tool closed up with the splash guard 23 and the door 24. For this reason, if the door is opened immediately after the termination of the cutting, the misty cutting fluid would run out of the machine tool through an opened door portion, resulting in the pollution of the outside of the machine tool with the cutting liquid and/or the chips.
Specifically, the scattered cutting liquid and/or chips exert the following influences on the machine tool and others.                Adhesion of the chips to an empty tool pot or a standby tool of the tool exchanger makes a tool exchange operation difficult, leading to the degradation of a cutting accuracy.        When the cutting liquid and/or chips are scattered on the inside of the machine tool, adhesion of the scattered cutting liquid and/or chips to a window of the splash guard makes it impossible to check to see the inner conditions of the machine tool.        Adhesion of the cutting liquid to resin- or rubber-made parts degrades (such as swelling and hardening) these parts, whose mechanical properties will be lost, leading to damages to these parts.        Adhesion of the cutting liquid to a machine tool portion coated with grease degrades or sweeps away the grease, leading to the development of defects attributable to an insufficient lubrication.        An operator who opened the door in front of the machine tool may inhale the misty cutting liquid.        When the cutting liquid is released out of the machine tool, adhesion of the released cutting liquid to a floor surface creates a dangerous slippery working environment.        
In this connection, there is provided a variety of methods for preventing the chips and/or cutting liquid from being scattered, in addition to the above method that employs the splash guard and the mist collector. For instance, in Japanese Patent Application Laid-open No. 62-74546 and No. 2000-94261 and Japanese Utility Model Registration No. 2592097, a method is disclosed, in which there is provided a spindle head mounted with a cutting liquid feed device, which is adapted to discharge a cutting liquid in a circular shape, thereby allowing the cutting liquid to provide a shower curtain for preventing the cutting liquid and/or the chips from being scattered.
In the above conventional method wherein a shower is formed with cutting liquid around the tool and the spindle in order to prevent the cutting liquid and/or chips from being scattered, the cutting liquid feed device for providing the shower curtain of the cutting liquid is mounted to the spindle head. For this reason, the weight of a spindle part increases, resulting in the degradation of the acceleration/deceleration performance of the spindle part, which leads to a decreased productivity. The above method also needs to stop the feed of the cutting liquid in case of exchanging the tool. Accordingly, it is feared that the misty cutting liquid having been confined in the shower curtain might be scattered outward. It is also feared that the cutting might be started before a shower curtain is formed again subsequent to the exchange of the tool, thereby causing the misty cutting liquid to be scattered into the splash guard. If an operator starts cutting on confirming the formation of a shower curtain subsequent to the exchange of the tool in order to prevent the misty cutting liquid from being scattered, a cutting time will be prolonged, leading to the decreased productivity.
Furthermore, in the above method, the cutting liquid feed device is moved together with the spindle during the cutting operation, so that a distance between the cutting liquid feed device and the workpiece varies. Although a length of the shower curtain also varies with the movement of the cutting liquid feed device as the spindle is moved in the axial direction thereof, the volume of a space enclosed with the shower curtain tends to be kept constant. Thus, a variation in shower curtain shape occurs. As a result, the above method involves a problem in that when the spindle is moved away from the workpiece, for instance, shrinkage of the shower curtain (in other words, shrinkage of a sectional area of the shower curtain as viewed in a plane orthogonal to the tool axis in the vicinity of the workpiece) arises to such an extent that the shower curtain makes contact with a revolving part of the spindle and/or the tool, thereby causing the cutting liquid to become mist. In addition, there is a limit in the length of a shower curtain for stable formation of the shower curtain. Thus, if a tool equal to or longer than such a shower curtain is in use, a passage will be opened up through the shower curtain. It is thus feared that the chips and/or the misty cutting liquid might run out of the shower curtain through the passage thereof. Furthermore, in a horizontal-type machine tool with the spindle having an axis in parallel to a horizontal direction, there is a limit in the length of a shower curtain for stable formation of the shower curtain under the influence of gravity. Thus, all that is attained is a small-length shower curtain. Accordingly, the above method is not supposed to be suitable to the horizontal-type machine tool.